Women and children injured by stray bullets and mortars during fighting in the Somali capital Mogadishu are being turned back at military checkpoints as they try to reach hospitals, the United Nations children's agency said yesterday.

Describing the humanitarian situation in the city as the worst since 1991 - the last time Somalia had an effective government - Unicef's representative for the country said the restrictions meant "people are being left behind in the streets to die". The roadblocks are manned by government and Ethiopian troops, who are battling to contain a growing insurgency.

"The lack of respect for basic humanitarian principles from all sides is horrific," said Christian Balslev-Olesen. "It's violence, harassment ... terror against the civilian population."

The conflict has already forced 600,000 people, more than half Mogadishu's population, to flee the city since February. More than a third of those fled in the past five weeks as fighting escalated.

Hopes of a ceasefire are dim. Somalia's transitional government has made little effort to reach out to political opponents or the guerrilla fighters, who in turn have vowed to fight until the Ethiopian occupation ends. The insurgency is broad-based, comprising remnants of the Somali Council of Islamic Courts (SCIC), chased out of Mogadishu by Ethiopian forces last December, as well as militias controlled by warlords opposed to the government.

Ethiopia and the United States, which backed the move to oust the SCIC citing alleged links to al-Qaida, say a large international peacekeeping mission is the answer. But no countries appear willing to add to the 1,600 Ugandan peacekeepers confined to a small area of Mogadishu.

The abuses by government forces and the insurgents fit the pattern of impunity that has plagued Somalia for 16 years, and UN officials and diplomats admit they have little leverage over either party. Ethiopia, however, should be a different matter.

Speaking to the Guardian a few weeks ago, the Ministry of Foreign Affairs in Addis Abada denied its troops were guilty of abuses. "Our conduct of war is in line with international law," said Wahide Beleye, spokesman for the ministry. "We don't target civilians."

But UN officials insist that reports of indiscriminate shelling and heavy-handed house-to-house raids are credible.

"Ethiopia has a functioning government that should be accountable," said a senior UN official responsible for Somalia, who cannot be named for fear of compromising his agency's work. "We tried talking to Ethiopia, even at ambassador level, but we get nowhere. It seems that they, like the other parties, can get away with anything in this dirty war."

Besides the blocks on medical access, Unicef said that both government-allied militias and insurgents were recruiting children to fight. It also noted an unprecedented amount of sexual violence against women, particularly at checkpoints.